The European Court of Justice (ECJ) has often been characterized both as a motor of integration and a judicial law-maker. To what extent is this a fair description of the ECJ's jurisprudence over more than half a century? This book, divided into two parts, examines this question. Part one develops a new heuristic theory of legal reasoning which argues that legal uncertainty is a pervasive and inescapable feature of primary legal material and judicial reasoning alike, which has its origin in a combination of linguistic vagueness, value pluralism, and rule instability associated with precedent....